The present invention relates to an image processing apparatus, and more particularly, to a device and method for binarizing pixels by removing isolated points.
Generally, an image processing system, such as a facsimile machine, compares a mean brightness value of local pixels with a brightness value of a central pixel to determine the logic state in which a pixel is binarized. A binarization method of this type is disclosed in Korean Patent No. 93-3484, assigned to the same assignee as the present invention. This type of method is used in a facsimile machine for improving character readability by emphasizing edge regions in consideration of a brightness characteristic of local pixels. Such a method, however, applies uniform threshold values without consideration of the quality of the document being processed. Therefore, when documents of normal quality are processed, character readability can be improved. When documents of poor quality are processed, however, isolated black dots (i.e., isolated points) are generated on the white background of the document. In particular, when there is only a slight difference in brightness between the edges of the image and the white background of the document, in order for these edges to be cleanly displayed as black lines, the threshold value must be reduced. For example, when pixels exhibit 16 different levels of brightness, wherein level 16 represents a brightest level and level 1 represents a darkest level, the threshold value should be set to represent either level 1 or level 2. Doing this, however, creates a problem in that the possibility of generating undesired isolated points increases. The present invention is directed towards solving this problem.